The ever-increasing demand for multimedia content on end-user devices combined with the limited bandwidth available to deliver that content has lead to the development of very efficient and highly robust video coding algorithms. For example, the H.264/AVC (Advanced Video Coding) digital video coding standard written by the International Telecommunication Union (ITU) Video Coding Experts Group (VCEG) together with the International Organization for Standardization ISO/International Electrotechnical Commission (IEC) IEC Moving Picture Experts Group (MPEG) is widely known for its ability to provide high quality video in error prone environments. The emerging scalable extension of H.264/AVC, known as H.264/SVC (Scalable Video Coding) defines a scalable video bitstream that contains a non-scaleable base layer and one or more enhancement layers.
The H.264 standard contains a feature called Flexible Macroblock Ordering (FMO) that allows multiple “distinct slice groups” to be created in an H.264 picture in such a way that no macroblock (a block of 16×16 pixels) is surrounded by any other macroblock from the same slice group. Inside a slice group all macroblocks are ordered in raster scan order. Basically, each slice group is like its own little mini-picture. For instance, one slice group can be intracoded while a neighboring group can be predictively coded from the same corresponding slice group in a reference picture. The FMO feature makes it possible to take independent contributing streams from multiple sources and combine the streams together into one stream of composited pictures, say, for video conferencing.